The present invention relates to the field of synchrotron radiation devices, and more particularly to a synchrotron device having a particle track with at least one curved section.
Synchrotron radiation sources are known in which the synchrotron particle track includes a curved section containing a magnetic device having superconducting coil windings located on both sides of the particle track. The magnetic device surrounds a beam guiding chamber and is arranged in at least one cryostat having a vacuum housing. Further, there is at least one exit opening for the synchrotron radiation leading in an outward direction from the beam guiding chamber. A device is included for the mechanical fixation of the superconducting coil windings. A synchrotron radiation source of the type described above is shown in German Patent Application DE-OS No. 35 30 446.
It is well known that in the operation of a synchrotron, electrically charged particles, such as electrons or protrons are guided on a curved track and are accelerated to high energy by means of running often through high frequency accelerating fields. These accelerating fields are generated in a high-frequency acceleration cavity of an acceleration section of the track. In an electron synchrotron, the velocity of the electrons being introduced into the acceleration section already is near the velocity of light. Because the frequency of rotation is fixed, only the particle energy still changes. Synchrotron radiation is the relativistic radiation emission from electrons which are kept revolving at nearly the velocity of light on a circular track by being deflected in the magnetic field of a magnetic device. The synchrotron radiation furnishes X-radiation having parallel radiation characteristics and high intensity.
The synchrotron radiation can be used advantageously in performing X-ray lithography which is suitable for the manufacture of integrated circuits. The use of X-ray lithography produces structures which are smaller than 0.5 .mu.m. In the X-ray lithography process, parallel X-radiation having a useful wave range of about .lambda.=0.2 to 2 nm, strikes a mask that is to be imaged. Located immediately behind the mask is a semiconductor surface which is exposed by the radiation for the production of integrated circuits on the semiconductor chip.
In the German Patent Application mentioned above, one embodiment of an electron synchrotron of the so-called race-track type is illustrated. The race-track synchrotron has a particle track having alternating straight and curved track sections. In this embodiment, the radius of curvature is determined by the equilibrium between the centrifugal forces and the Lorentz forces in the field of the magnetic dipole devices. The magnetic dipole devices contain curved superconducting coil windings on both sides of the particle track. In each of the magnetic devices, the individual dipole coil windings are arranged together with a gradient coil in a cryostat. The magnetic devices, located in the cryostat curved track sections where the electrons revolve, keep the evacuated beam guiding chamber at a low temperature. Accelerating devices and an electron injector are associated with the straight sections of the synchrotron. The electron injector introduces electrons into the acceleration section.
In the known embodiment of a synchrotron radiation source, the beam guiding chamber is provided with a slot-like exit opening for the synchrotron radiation in each curved track section of the particle track. The Lorentz forces generated by the opposite superconducting coil windings attempt to push the legs forming the slot-like exit opening together. Therefore, the legs of a mechanical C or U-shaped support structure must be capable of countering these forces to keep the slot-like exit open. The superconducting coil windings must not undergo a position change under the action of the Lorentz forces. Such a position change would create a corresponding field distortion. Therefore, an elaborate mechanical fixation of the coil windings corresponding to the action of the forces is absolutely necessary. In the vicinity of the slot-like exit, this is extremely difficult. However, one device, as described in German Patent No. 35 11 202 compensates for the forces which push the slot together by using special, pretensioned clamping and tightening elements.
It is therefore an object of the present invention to provide a synchrotron radiation source having a relatively simple fixation of the superconducting dipole windings of the magnetic devices in the exit area of the synchrotron radiation.